Try this:
Set wmi = GetObject("winmgmts://./root/cimv2")
Sub TerminateScript(name)
qry = "SELECT * FROM Win32_Process WHERE CommandLine LIKE '%" & name & "%'"
For Each p In wmi.ExecQuery(qry)
p.Terminate
Next
End Sub
TerminateScript "Second.vbs"
TerminateScript "First.vbs"
WScript.Quit(0) 'terminate self